1. Field of Invention
This invention relates generally to devices for environmental remediation and, more particularly, to devices utilizing non-traditional energy sources and/or programmable logic controllers for environmental remediation.
2. Description of the Related Art
A general object of the present invention is to provide devices that are useful for environmental remediation. More specifically, these remediation devices can be operated at a distance from a local power grid by utilizing non-traditional energy sources, and further utilize programmable logic controllers (PLC) for off-site monitoring and operation of the devices
Environmental remediation is necessary, for example, where groundwater and soil have become contaminated, thus presenting an ecological threat to the environment. Methods of environmental remediation include, but are not limited to methods for recovery of free product from ground water, recovery of ground water itself, and aeration of groundwater or soil, air extraction from the soil and chemical or nutrient addition to the groundwater or soil. Each of these methods are effective in destroying or removing certain categories of contaminants from groundwater or soil.
Free product recovery is generally the process by which contaminated water, light or dense non-aqueous phase liquid contaminants are recovered and are then either processed through a treatment facility, or disposed of accordingly. Such contaminants are frequently, but are not limited to, separate phase volatile organic compounds (VOCs) such as petroleum hydrocarbons and chlorinated solvents. Recovery or destruction of contaminants can be achieved by utilizing compressed air to power a pump situated in a ground water well. Thus, the free product is directly removed from the ground water and temporarily stored above ground in a tank prior to disposal. By removing contaminant mass from the subsurface, the contamination is reduced. Free recovery has been found to be more efficient if the recovery pump is operated on an intermittent schedule. The most efficient recovery has been found to occur when free product is removed quickly, the product pump is turned off, the free product is allowed to return to it""s static level in the well, and then the free product is pumped off again.
Aeration systems, such as bioventing and air sparging, are bioremediation and mass removal techniques used to treat soil contaminated with VOCs. The use of injected air in the subsurface is called aeration. Aeration can be used to remediate soil contaminated by releases of petroleum hydrocarbons, chlorinated solvents and other VOCs. Aeration reduces contamination levels by two mechanisms, one biochemical and one physical. In the former, the injected air increases the amount of oxygen in the subsurface, stimulating the growth and metabolism of indigenous microorganisms. These microorganisms use the contamination as an aerobic energy source, producing carbon dioxide and water as by-products. This process is known as bioremediation. In the second mechanism, the flow of air through contaminated soil forces VOCs into the air stream. Once entrained in the air stream the contaminants are removed from the subsurface by adjective flow and are typically recovered by vapor extraction wells for destruction. This process is called mass removal.
Generally, these two mechanisms are brought about by different airflow regimes. Bioremediation is stimulated by relatively lower airflow, while mass removal requires higher air flow. In either scenario, air is introduced into the subsurface by pressurizing a vapor well with compressed air. Air will flow from the higher pressure in the well through the well screen and into the subsurface formation. The ultimate disposition of the injected air is dependent upon the geology of the formation into which air is injected as well as the pressure gradient and flow rate.
Bioventing utilizes injections of oxygen into soil. Pressure and flow rates in bioventing systems are low to concentrate on maximizing aerobic degradation, and minimizing volatilization. Lower airflow creates the conditions necessary for bioremediation, which requires no secondary capture of mobilized VOCs. At higher airflow, bioventing can be used in conjunction with a soil vapor extraction (SVE) system to mobilize, and then remove soil contamination. Typical pressure and flow rates for bioventing systems are, 5-10 psi (34.5-68.9 kPa) and 2-6 cfm (57-170 lpm), respectively.
Air sparging is very similar to bioventing. Air sparging systems inject air into ground water as opposed to soil, and sparging systems work toward both aerobic degradation and volatilization. Air sparging systems generally have higher pressure and flow rates to overcome the pressure of the water column. Operationally, the air must be pumped into the injection well at a pressure sufficient to displace the water column and overcome frictional losses in the system and capillary resistance to the air entering the aquifer. The injected air will form a shape in the saturated zone that approximates an inverted cone. The dimensions of this cone are determined both by the geologic characteristics, especially grain size, of the saturated zone and the rate of flow of injected air. Operators of the sparging system can control air flow, i.e. volumetric flow rate, pressure, velocity. Typical pressure and flow rates for air sparging systems range from 5-50 psi (34.5-344 kPa) and 4-10 cfm (113-283 lpm) respectively, depending on soil type, depth to water column, radius of influence, and degree of volatilization. FIG. 1 shows how air sparging and SVE systems work together to reduce contamination. Neyer and Sutherson (1993) Air Sparging: Savior of Ground Water Remediations or Just Blowing Bubbles in the Bath Tub; GWMR. 
A vacuum can be used under either scenario described above to increase air flow and aid in remediation. In the aeration scenario, lower airflow creates the conditions necessary for bioremediation, which requires no secondary capture of mobilized VOCs. At higher airflow, a vacuum can be used to mobilize and then remove soil contamination.
Injection of chemicals or nutrients into groundwater or soil is also a commonly applied remediation technology. Typically a liquid or foam is directly injected into a well from an above ground tank. By injecting appropriate chemicals or nutrients, biological growth may be enhanced to increase the remediation or consumption of the contaminants.
In addition to utilizing effective environmental remediation techniques, the present devices rely on non-traditional power sources. This is advantageous in many ways including, but not limited to that these devices can be installed in any location where a power supply necessary to run traditional systems is not available or is expensive to use or install, and the non-traditional power sources, such as solar panels, operate without fuel, waste or pollution. Further, the device""s relatively simple construction makes installation relatively simple.
In addition to utilizing effective environmental remediation techniques, the present devices utilize PLCs for allow remote operation, monitoring and automated data collection. Remote monitoring saves cost of on-site inspections by technicians. Data collected may include, but mot be limited to, cumulative free product recovered, product and water levels in the well and air compressor run time, pressure and flow rate of the pump.
In accordance with one aspect of the present invention, these and other objectives are accomplished by providing a remediation device being non-traditionally powered and having a PLC to control the frequency and duration of system operation.
The above described and many other features and attendant advantages of the present invention will become apparent from a consideration of the following detailed description when considered in conjunction with the accompanying drawings.